(Hydra species; Credit: Oinari san)
Some animals and plants that reproduce asexually "can in principle achieve essentially eternal life," according to a University of Gothenburg press release.
Scientists at the university are studying such species to find out how they avoid aging. So far, one chemical appears to be key: telomerase. This is an enzyme that protects DNA. It is more active in the longest-lived people, so its benefits likely extend throughout the animal kingdom.
The animals that can possibly achieve immortality under ideal conditions, such as sea squirts, certain corals, Hydra, and Turritopsis nutricula (the immortal jellyfish), often activate telomerase. Helen Nilsson Sköld of the Department of Marine Ecology, University of Gothenburg, and colleague Matthias Obst are studying sea squirts and starfish to learn more about how these marine creatures seem to ward off aging.
Out of the animal immortality A-list, sea squirts and starfish have genes that most closely resemble those of humans.
"Animals that clone themselves, in which part of an individual's body is passed on to the next generations, have particularly interesting conditions related to remaining in good health to persist," Sköld was quoted as saying in the press release. "This makes it useful to study these animals in order to understand mechanisms of aging in humans."
"My research has shown that sea squirts rejuvenate themselves by activating the enzyme telomerase, and in this way extending their chromosomes and protecting their DNA," she added. "They also have a special ability to discard 'junk' from their cells. Older parts of the animal are quite simply broken down, and are then partially recycled when new and healthy parts grow out from the adult bodies."
Starfish are also amazingly immune to problems that affect the rest of us. If they lose a body part, for example, many species can simply grow another one. Reproduction involves tearing apart their bodies, somewhat akin to growing a new plant from a broken off piece of a "mother plant."
Eternal life, from an evolutionary standpoint, however, has a big drawback. Due to asexual reproduction, the species as a whole retains very low genetic variation. This means they could be particularly vulnerable to climate change and not enjoy immortality after all.
Scientists are therefore rushing to study such species, which may hold the secrets of increasing our own longevity. It would be a colossal human mistake if our pollution, habitat encroachment and other activities erased our chances of learning more about nature's anti-aging secrets.